A dc converter is described in J. Wustehube, "Circuit Components", 1982, expert publication/VDE-Publishers, Series Contacts & Studies, Vol. 33, page 26. This converter, utilized to supply electronic and electrical devices, sums a feed voltage supplied to the converter and additive voltages generated by the converter itself by rectification to form a main output voltage in this system, pulse-width control serves to regulate the primary current flowing through a primary winding of a converter transformer through the use of a switching transistor.
The circuit described in this publication is capable of delivering a constant output voltage, especially to sensitive electronic devices, even upon the development of sharply varying feed voltages and feed voltages which are greatly different from one another.
Another advantage of the converter is that it can be set for simultaneously outputting a number of output voltages including a main output voltage which can be regulated to be exactly constant, as well as auxiliary output voltages which can vary to a greater or lesser extent with fluctuations in the feed voltage.
The regulatory range of a converter of this type is in principle wide enough to allow all customary line voltages (for example from 100 volts to 240 volts) to be rectified without switching because of voltage differences, the rectified line voltage being supplied as the feed voltage to the converter input.
In practice, however, the efficiency of the converter and, of course, the constancy of the various auxiliary output voltages will reflect the fluctuations of the input voltage.
With the increased stringency of the voltage supply requirements of more modern electronic devices, this type of dc converter is rapidly becoming unusable and can only be amplified effectively if it is switched off, or provided with additional means for responding to widely varying line voltages which may be applied to the converter.